Ook, OoK or OOK may refer to:

• Ook Chung (born 1963), Korean-Canadian writer from Quebec
• On-off keying, in radio technology
• Toksook Bay Airport (IATA code OOK), in Alaska
• Ook language (Discworld)
• Ook!, an esoteric programming language based on brainfuck
• Ook, the mascot and name for Northern Alberta Institute of Technology sports teams

• Early Christmas Morning (Cyndi Lauper song)
• Early church
• Early Church Father
• Early Church Fathers
• Early cinema
• Early civilization
• Early climax
• Early College Academy
• Early college high school
• Early College High School (Costa Mesa, California)
• Early Commemoratives
• Early completion
• Early Completion
• Early Computer Works
• Early computing devices
• Early conceptions of the channel tunnel
• Early conceptions of the Channel Tunnel
• Early Conceptions of the Channel Tunnel
• Early congenital syphilis
• Early Congolese History
• Early congolese history
• Early cyrillic alphabet
• Early Danubian culture
• Early Day miners
• Early day Miners